Field of the Invention
The invention generally relates to a wireless communication technology, and more particularly, to a wireless communication method for determining whether to be restricted in the concatenation rule according to the type of the length indicator.
Description of the Related Art
Multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrums, and integrating better with other open standards using OFDMA on downlinks (DL), and SC-FDMA on uplinks (UL) and multiple-input multiple-output (MIMO) antenna technology.
FIG. 1A is a block diagram of a conventional control plane protocol stack in a wireless communications device and a LTE network. The wireless communications device includes a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a medium access control (MAC) layer and a physical (PHY) layer. The network includes a RRC layer, a PDCP layer, an RLC layer, a MAC layer and a PHY layer. The layers shown in FIG. 1A may be divided into a first layer (Layer 1), a second layer (Layer 2), and a third layer (Layer 3) based on three lower layers of a well-known interconnection scheme, such as an Open System Interconnection (OSI) reference model. FIG. 1B is a block diagram of a conventional user plane protocol stack in a wireless communications device and a LTE network. The wireless communications device includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a medium access control (MAC) layer and a physical (PHY) layer. The network includes a PDCP layer, an RLC layer, a MAC layer and a PHY layer. The layers shown in FIG. 1B may be divided into a first layer (Layer 1), a second layer (Layer 2), and a third layer (Layer 3) based on three lower layers of a well-known interconnection scheme, such as an Open System Interconnection (OSI) reference model.
In the LTE standard, there are some standards for RLC Service Data Unit (SDU) and RLC Protocol Data Unit (PDU) in the RLC layer as below. As shown in FIG. 2, an RLC PDU comprise two parts, head and data field, wherein the head comprises a plurality of length indicators (LI) for in indicating different RLC SDUs or RLC SDU segments in data field. Each of the RLC SDUs or RLC SDU segments should be indicated by a length indicator in an RLC PDU, instead of the last RLC SDU or RLC SDU segment, i.e. the last RLC SDU or RLC SDU segment does not need the length indicator. The length indicator indicates the length of an RLC SDU or RLC SDU segment in an RLC PDU.
Before the LTE standard of release 11 (R11), the length of the length indicator was 11 bits (11-bit length indicator), and the length indicator can only present a length of up to 2047 bytes for an RLC SDU or RLC SDU segment. Therefore, an RLC SDU or RLC SDU segment should be mapped to the end of the data field of the RLC PDU if its length is greater than 2047 bytes. Taking FIGS. 3A-3B for example, if the length of the SDU#3 is smaller than or equal to 2047 bytes (as shown in FIG. 3A), the SDU#3 will not be mapped to the end of the data field of the RLC PDU, and the SDU#4 can be concatenated with the SDU#3. If the length of the SDU#3 is greater than 2047 bytes (as shown in FIG. 3B), the SDU#3 will be mapped to the end of the data field of the RLC PDU and the SDU#4 needs to be mapped to the next RLC PDU.
In the LTE standard of release 12 (R12), the 15-bit length indicator can be configured, it can represent a length of up to 32767 bytes (the max length of RLC SDU is 8188 bytes) for an RLC SDU or RLC SDU segment. However, in the current LTE standard, the concatenation rule is still restricted in the RLC layer. That is to say, even an UE supports 15-bit length indicator, an RLC SDU or RLC SDU segment still should be mapped to the end of the data field of the RLC PDU if its length is greater than 2047 bytes. Taking FIG. 3 for example, for 15-bit length indicator, if the length of the SDU#3 is greater than 2047 bytes, the SDU#3 will still be mapped to the end of the data field of the RLC PDU and the SDU#4 still needs to be mapped to the next RLC PDU.